So I wrote a question a little earlier about the differences in mindset between people born from planetside colonies vs. those born in space [it's linked to save me from explaining the whole system - please tell me if this is wrong, I'm new] [here is the link: Differences in mindset between people born in space and people born planetside].
Anyways, so I was also wondering if there would be any physical differences. There is a lot of travel between planetbound and spacebound colonies, but a lot of people also stay in one place for their entire life, and some groups stay for generations.
As I said in my other question, there is artificial gravity in space, but it's less than the regular true gravity on planets/moons [the levels of which would vary]. People in space get access to fresh plant-food [that's what I'm calling it] since flora is grown via hydroponics and LEDs. People born planetside are exposed to sunlight [through the windows of their habitat of course], and have a small amount more space.

For reference, these people have been living in these ways for a coupla' hundred years, so not a huge amount of time in evolution's terms [though I guess there is evidence of certain species evolving a lot faster than considered normal].
A few differences I can think of could be height [less gravity = more allowance to grow taller], muscle mass [less gravity = less strength required to move], slight differences in colouration [more sun exposure = more melanin], differences with eyes [smaller environment + long time spent there = eyes working better up close], and maybe something with circulation as a result of the way the "gravity" is distributed in a centrifugal spinny thing. I am more asking about changes to biology as a result of living in that environment, even if they are un-seeable or minor, not really changes in genuine health or appearance.
Are there any differences I may have missed?

  • $\begingroup$ I know I posted a question already today, but I thought it was unclear and badly worded, so I'm going to come back to it a little later when I've figured out what I want to say. $\endgroup$
    – sprout
    Commented Nov 7, 2021 at 11:05
  • $\begingroup$ It looks like you're looking for help brainstorming ideas for your world rather than asking a specific answerable question. Questions like this with many valid answers are too broad for this site. Can you edit your post so that you're asking a single more specific question? $\endgroup$
    – sphennings
    Commented Nov 7, 2021 at 12:10
  • $\begingroup$ This is the SE Meta post on limits for questions. I am not sure if the WB.SE has its own rules regarding the number and frequency of questions the user may ask (I did not find any). || I do not think that this question is too broad or unspecific. However, it would be better to reword your question in such a way that it does not ask for ideas (this community does not like it). It would also help if you could include your research. [cont.] $\endgroup$
    – Otkin
    Commented Nov 7, 2021 at 17:02
  • $\begingroup$ [...] Please note that the WB.SE is not meant to be a place where world creators start their research. It is presumed that questioners did research on their own but met some difficulties or problems with understanding and/or application of their research and then came to the WB.SE to ask for help with these particular difficulties/problems. In other words, it is expected that you already know something about potential physical differences and are seeking to verify your conclusions or checking if you have missed something. $\endgroup$
    – Otkin
    Commented Nov 7, 2021 at 17:09
  • $\begingroup$ @Otkin I should probably reword it anyways since I don't want people to get confused. I've tried to do research on the rest of the internet but it isn't helping since it's a weirdly specific question, so I thought I might ask you people. I will edit it when I can :) $\endgroup$
    – sprout
    Commented Nov 7, 2021 at 20:31

3 Answers 3


For starters, think of the long-term impact of lower gravity settings on the human body. Humans lose bone density, and muscle strength since less is needed in lower gravity. Over generations, perhaps people in space bound colonies would be smaller.

Also, diet is important to consider. It seems plants are more sustainable than meat for space-bound colonies. Consider the long-term impact of plant-based diet, such as B12 deficiency.

  • 1
    $\begingroup$ Huh, okay. Being smaller might also help moving around in more cramped spaces. $\endgroup$
    – sprout
    Commented Nov 8, 2021 at 1:13
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    $\begingroup$ Meat can be produced artificially. We can do it now. There is no reason to believe that human civilisation capable of building huge space habitats is unable to produce artificial meat. $\endgroup$
    – Otkin
    Commented Nov 8, 2021 at 3:55
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    $\begingroup$ They do grow artificial meat, however not everyone eats it :) $\endgroup$
    – sprout
    Commented Nov 8, 2021 at 4:36
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    $\begingroup$ @sprout You can also do aquaculture. Tilapias, IIRC, can be raised in a very limited space. $\endgroup$
    – Otkin
    Commented Nov 8, 2021 at 4:55
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    $\begingroup$ @Otkin Oooh, I'll have a look into that :D $\endgroup$
    – sprout
    Commented Nov 8, 2021 at 5:12

If you're using the original specifications for O'Neill Cylinders as a stepping off point then your Space Born are going to have a series of slight differences stemming from the fact that they live in an atmosphere with a sea-level oxygen pressure but total pressure closer to that at 5500 metres above sea level. This will effect the structure of their skin, lungs, eyes, ears, mucus membranes, and heart, but not in massive or immediately obvious ways. Any experience with the thicker air of sea level on Earth would likely be extremely uncomfortable, possibly lethal. At the minimum they'd be rapidly fatigued, unless and until they had time to adapt, as their chest muscles worked overtime to move twice the weight of air for the same amount of O2.

Their sense of balance may be very different if they live under spin induced pseudogravity depending on the diameter of their habitats due to their degree of Coriolis compensation being different to those on planets.

There is a lot of debate as to the exact effects of lower gravity on long term musculoskeletal development but I would expect that anyone born and raised in micro-gravity is going to have lowered bone and tissue densities. This will probably make them relatively weak and breakable, but if their home habitat is kept at Earth gravity then this shouldn't be a cause of difference.

Skin pigmentation could go either way depending on the typical UV load. It should be noted that at present one of the most promising class of foods for space grown food rations are fungi. Most fungi are naturally high in bio-assimilable Vitamin D so Space Born may tend towards higher skin pigmentation than one would otherwise expect, more Melanin in the skin means less Vitamin D production when exposed to UV radiation.

Eyesight could go in a number of directions, I can make arguments for either greater or lower light sensitivity, colour perception, distance optimisation, etc... depending on the exact details of life in space.

  • $\begingroup$ I didn't think of oxygen pressure, I'll certainly be looking into that :) Thanks for the answer! $\endgroup$
    – sprout
    Commented Nov 8, 2021 at 5:31
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    $\begingroup$ @sprout O'Neill engineered based on an atmosphere that was half the total pressure of Earth at sea level but with the same partial pressure of oxygen so people could still breath normally. For physically mature earthlings heading into orbit that wouldn't make much of a difference but people born under that regime are going to develop differently. $\endgroup$
    – Ash
    Commented Nov 8, 2021 at 7:00

Okay, I tried to hint at that in the comments but it seems I need a little bit more Space.

No difference

There are at least 4 reasons, why I think that way:

  • health reasons, aka how biology works
  • environmental reason, why and how we would like to move in space
  • technological reasons, what we are capable of doing in space
  • Today's reality - on this planet, there are people of all shapes sizes, and a variety of colors - so different from who - all of them? Why?

Health, biology

This one is tricky to explain, and sure it is rather my perception aka opinion.

Let's take this one as an example before I bring some more complex generalizations

It is quite a known thing that vision suffers in microgravity, due to a change of liquid redistribution in the human body. The pressure difference, which we talk about - it is in a hundred pascals, this much heart is capable of to create, or even less. It leads to excess pressure in eye-ball, which leads to distortions and potentially permanent damage(this one is my guess based on other things)

The problem is just one example, which is chosen for it being known, the fact it is hard to do anything about it with our current means(unsolved yet for decades), but the reason for it also appears to be simple and it could be fixed if we had better means to address such problems.

So it's funny to make up fancy stuff like muscles this or that differences - to amuse readers and viewers, preferably producing elf-like creatures cuz it sells better, but it not funny to have anemia because of your Osteoblasts and Co do not develop proper ways, leading to dysfunctions of blood-producing parts. (problem with bones is real, but potential anemia due to that I do not recall it firmly, maybe it just my imagination)

Now more general statements:

a human body is capable to endure a lot, but it needs to understand that it, the body, did develop from a Single Cell, a process called ontogenesis in general, which includes embryogenesis as well(at least by me). This is an amazing process - it is something wonderful - but all kinds of minor deviations do produce all kinds of mistakes in it. It is robust to many factors, which we have here on earth, but it is also selectively weak against the factors which we may have here on earth.

Meaning the development process is quite a sensitive thing, and it is possible to be sensitive especially for factors that we do not have on earth, and this sensitivity and results of it will be, most likely for reasons of the evolution process, to be negative. Reasons for that can be imagined as - there are too many things to break, but there is only one good result to have, as if it would be another way around evolution would skyrocket and would be easy as pie, but no it takes millions of years, millions of generations. Reasons can be expressed in more formal terms, but not the point.

In general - one has to protect that development process to have healthy humans, and if one can't do that, there is no place in space for them - it is the current motto of any space agency, and there is no point in changing that in the future for them or groups of people - we are looking for better future, a regular one - we already have it. And we move in space for that better future now, or else there is no point.

This brings us to the next reason:

Environmental reason

  • why and how we would like to move in space

There already are reasons to recreate a proper environment for humans in space, as health reasons, but it goes along with other reasons as well.

We would like to have a nice place to live, because if it is not nice - we already can have that in any place on Earth.

To have "a nice place to live" - it includes a lot of stuff, how it looks, how it feels, its size, how many people there are, and such.

For psychological reasons, for biological reasons, for healthy society(as society) reasons, it makes sense to have an environment that resembles or feels like a good place on earth.

One can imagine some tin can, submarine situation - but if billions of people are not capable to change it for the better - they deserve that - I mean it is within their capacities to make a good environment, and it is that ways from the very beginning - because it can and should be the attraction for all those people who decided to move from earth to space, in initial migration wave.

With O'Neil principle aka concept aka cylinders - just as an idea, but a better implementation, not like it was envisioned back then(cuz critical mistakes were made) - but the scale and stuff - hundred thousand, millions of people per space hab, with enough space for people, and recreation of nature there.

Yes, not everything can be recreated, but I as city dwellers do not care - if there are some forests to move once in a few years - I call it good enough. Real nature lovers, active sky cave divers, and such - please stay on earth, keep an eye on it.

Apparent gravity and pressure and light(spectrum) and such - can be recreated and there are reasons to invest efforts in doing so.

All that possible to make with technologies which are available today, but also it brings us to technologies potentially available in the future:

Technological reasons

  • what we are capable of doing in space and because of space

Today one of the emerging technologies is generative design - it comes as a pack with neural networks and simulations of physical processes and digital design practices.

In essence, it is the automation of finding solutions and implementations for our practical needs.

  • quite a good depiction of such a system was that expert system from the Iron Man movie(first one and it emerged a few times later as well) when Tony asks it to make something that he envisions, and it does. For those who paid notice to it.

It is a powerful tool, it can be, maybe less in the way as it was envisioned in the movie, but it can be as effective as that one.

And there is another cluster of problems - protein folding simulations used in medicine and not only there - to make better stuff, find useful stuff, and such.

All that together connected with nanotechnology, elements of which we have today, in technological fields so as in biological, medical applications (have or envision to have)

All mentioned processes are, at the moment, CPU-hungry processes and due to this and other factors may not be so cheap. And that(or a different one) Big Computer In Space once implemented can make a significant push to the technologies development.

As one of the well-recognized technologies are gray goo like nanotech, it is desired by many(I guess) even if some not so well informed authors maybe had a bad influence on the perception of it by the public, in the past - but I guess not many will deny advantages of such technology.

  • what a right implementation and right use of it can be is a different topic and it has some stuff that needs to be understood correctly to imagine a correct picture and many do it wrong. But fixing that is out of the scope of this answer.

So having put K1 energy in technology development, it would not be surprising to have plenty of good technologies to use, including, nanotech which is quite a universal tool - as for environment creation so for health keeping, maybe finally we will live for few hundred years after that. (I mean there are incentives besides space-related ones)

  • I know some people classify nanotech as magic stuff, good to have, never will happen - okay, let's address that without nanotech

It is certain that thanks to technologies we have today if we have an opportunity to use them on a greater scale, the aforementioned K1 energy budget will accelerate our development, and improve our technologies in a big way. (Not a singularity)

With such an energy budget - there is also no apparent reason to imagine that some significant portion of people in space will have lack access to those technologies (most of them) and have any difficulties in this aspect.

They do not have a lack of energy, because of sun and microgravity(for curious, this) - and it has big consequences on production, the efficiency of production becomes less relevant, to a certain acceptable degree, than it is now on earth, at least you for sure won't bother about 5-10% difference and consider convenience and practicality in the first place and efficiency difference in the second place.

  • I mean, as of today, the depiction of space capacities in sci-fi is lacking accuracy in a big way, it is understandable it is easier that way to make plots and such, and reuse special effects and writers from different areas of entertainment production.
  • ISS problems scale badly for the sizes of millions of people in space. I mean a station for a million people is a totally different beast than ISS.

The explanation is not full and probably lacking, but as-is - I did my part, but if you investigate space, instead of handwaving problems, then it may be a better work, try to not fall victim to usual tropes as many of them make no sense, and if you will, never mention me, lol.

People of the Earth, as of today

This is the shortest one - there are all kinds of people on this planet - short, long, big, small, etc.

Why? Because selection factor for a long time is about our intellectual capacities, not our physical body. (because we live in societies)

If you can distinguish USA citizens, then sure, you will notice a difference in the appearance of space folks - as they will be descendants of those who moved in space and it will be not everyone, maybe, depends on your story, how did they move in space.

Etc. I guess you can think along the lines on your own. Difference from who, if we already have all kinds and shapes.

Didn't mention it in the biology section and will do it now. There is another group of people, who imagine making biological modifications for everything, to adapt that way - meaning introducing changes deliberately.

A big topic on its own, but rather exception, because of the convenience of technological solutions in that regard, there is no need for special adaptations as long as we have technological means to solve problems and create proper conditions for ourselves. The advantage and convenience of technological solutions are in that one can change them at will easily - space suit is one of such technological means - which can be worn and un-worn(?). A car, tank, airplane - also are such solutions, meaning technological means are universal, while biological adaptations are not.


This way, I have reasons to think - there is no reason for any difference to exist. And are reasons to solve problems even if there are some factors. And people are well capable to do so.

  • $\begingroup$ That was an interesting read, and I think I get where you're coming from. Thankyou for your contribution :) $\endgroup$
    – sprout
    Commented Nov 8, 2021 at 10:00
  • $\begingroup$ @sprout yes, my motto is space for a better life for humans in space and on earth, or it is not worth it. And all things I look at telling me it is possible to make it that way - a better life and for people in space and for those who stay on earth. It's probably better for those who are in space, but yeah, who I'm to judge, lol, earthlings will get a good share of the fun/profits it's just that their planet isn't big enough to fit it all. $\endgroup$
    – MolbOrg
    Commented Nov 8, 2021 at 14:59
  • $\begingroup$ Yeah, you have a point. I wouldn't necessarily say changes in environments [and biology to adapt to those environments] would be negative, though. They're just differences :) $\endgroup$
    – sprout
    Commented Nov 8, 2021 at 20:58
  • $\begingroup$ @sprout minor in 50 generations mostly as result of recombination of existing genetic pool(so not really new) and if you let people die, like in medieval Europe, letting sufficient child mortality to happen - for selection to work, or do eugenics and be strict who marries whom, or artificial wombs and precalculate stuff based on gene sequencing - 5-10 generations - difference won't exceed stuff one can get by training, best case scenario. 50 generations - the number comes from a selection experiment conducted on foxes in Russia, for purposes of their domestication. $\endgroup$
    – MolbOrg
    Commented Nov 9, 2021 at 8:16

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